A conventional ceramic whetstone, as shown in FIG. 1 is usually made of hardened ceramic powder. The ceramic whetstone (1) includes a handle (10) and a ceramic stick (11) fixed to a first end of the handle (10). It is lighter, stronger for sharpening cutlery than conventional metal whetstone. It costs higher, and is damaged easily. Meanwhile, whetstone made of compact ceramic grits may cause creep deformation to relieve stress.
Accordingly persons skilled in the art have provided some improvement, such as TWM310766 entitled “Hollowed out ceramic whetstone” (As shown in FIGS. 2 and 3) to Cheng-Hsien Shen on May 1, 2007, Shen taught the ceramic whetstone (2) comprising: a handle (20) and a ceramic stick (21), characterized in that a pedestal (22) incorporated to a first end of the handle (20), and flexible covers (23) disposed to both first and second ends of the pedestal (22), the stick (21) is hollowed out for fitting over the pedestal, and the flexible covers (23) resist against an inner wall of an axial hole (211) at both first and second ends respectively, the axial hole (211) is formed through the ceramic stick (21), and a cap (25) fit over a first end of the pedestal (22) to resist against the stick (21); thereby, the stick (21) and the pedestal (22) are integrally coupled together.
The ceramic whetstone has some drawbacks as following:
1. Since the handle (20) and the ceramic stick (21) can't be fixed securely, a metal pedestal (22) is inserted into the ceramic stick (21) and secures the ceramic stick (21) by two flexible covers (23). This implement adds extra weight to the ceramic stick (21), and the cost is high due to complex manufacture.
2. The ceramic stick (21) is manufactured by extrusion moulding in which a high quality of craftsmanship is required to reach a high straightness accuracy. Since a high quality of craftsmanship is not easy to apply, the metal pedestal (22) and flexible covers (23) are necessitated to improve the stability of the ceramic stick (21). However, insufficient straightness accuracy causes vibration of the ceramic stick (21) while sharpening the cutlery; this may lower the quality of sharpening and endanger the safety of the user.
3. The cap (25) fit over the first end of the pedestal (22), a nut (24) and a spacer (26) are added for screwing the cap (25) to the pedestal (22); once the cap (25) is loosely out of contact between the pedestal and the stick (21). It may cause the pedestal separated from the stick to induce damage or breaking down to the stick.
4. A handle (20) is shaped with an overall cylindrical surface, when put it on a table with inclined work surface, it is easy to rolling down to cause accidental damages.
5. A pedestal (22) is made of metal, rusted easily, if electric plated and coating required, may increase manufacturing cost.